1. Field of the Invention
The present invention relates to an exhaust control valve, and more particularly to an exhaust control valve for an electromagnetic pump, by which the pressure and quantity of exhausted oil can be maintained at constant levels, an incomplete combustion of the exhausted oil can be prevented and a loud noise, which is caused by exhaust of a high pressurized oil, can be prevented.
2. Related Art
An electromagnetic pump is an appliance for supplying fluid, and is generally used for supplying oil to a burner in a boiler system.
A conventional electromagnetic pump is operated as follows. Firstly, when an electric power is applied to a solenoid, a plunger assembly is moved upward so that oil is introduced into the electromagnetic pump from an oil tank. Then, when the electric power applied to the solenoid is cut-off, the plunger assembly is moved downward so that the sucked oil is pressurized. As the up and down movement of the plunger assembly is repeated, the pressurized oil is exhausted to a burner through an exhaust nozzle disposed in an upper portion of the electromagnetic pump. Meanwhile, when the pressure of the pressurized oil exceeds a predetermined value, some of the pressurized oil is returned to an oil inlet portion by a relief valve in order to control the pressure of the pressurized oil and is recirculated in the electromagnetic pump.
However, the conventional electromagnetic pump has the following disadvantages. Firstly, as shown as the letter "A" in FIG. 8, a highly pressurized oil having a pressure over a normal exhaust pressure P3 may be exhausted to the burner when the burner is ignited and thereby a loud noise is generated. In the present application, P1, P3, T1, T2, and T3 respectively mean an initial pressure, a normal exhaust pressure, a time when pressure of oil starts to increase, a time when a burner is ignited and a time when an oil having the normal exhaust pressure is exhausted.
Further, the biasing force of a spring to block an exhaust path of oil is so weakly set that the oil exhaust path is blocked-off belatedly after the operation of the pump has been finished. Accordingly, oil of low pressure may be leaked to the burner even after the operation of the pump has been finished. The leaked oil having low pressure is not completely burned by the burner and so it produces a bad smell.
To overcome the above described problems, another conventional electromagnetic pump is suggested, in which the pressure of a sucked oil is firstly controlled between a pressure control plunger and a guide rod, and is secondarily controlled by means of a relief valve, thereby loud noise which is generated due to exhaust of a high pressurized oil in a burner when the burner is ignited, can be decreased.
The construction of the conventional electromagnetic pump as described above is shown in FIG. 6.
As shown in FIG. 6, an electromagnetic pump 500 has a pump body 510. Pump body 510 comprises an inlet portion 512 for receiving oil from an oil tank, a first chamber 516 interconnected with inlet portion 512 through a first oil path 514, a second chamber 520 interconnected with both inlet portion 512 and first chamber 516 through a filter 540 and a second oil path 522 respectively, a third chamber 527 interconnected with both second chamber 520 and inlet portion 512 through a third path 524 and a fourth path 529 respectively, and a working chamber 526 in which a plunger assembly (not shown) is reciprocated.
A pressure control plunger 570 and a guide rod 580 are disposed in first chamber 516 interconnected with inlet portion 512 and a cover 600 is inserted in an open end of first chamber 516. A first spring 610 is disposed between pressure control plunger 570 and cover 600.
In addition, a suction check valve 550 and an exhaust check valve 560 are arranged in second chamber 520 in such a manner that they permit the oil to flow in the same direction. Working chamber 526 is interconnected with a fifth oil path 555 formed between suction check valve 550 and exhaust check valve 560 so that suction check valve 550 and exhaust check valve 560 are alternately opened and closed as the plunger assembly is reciprocated in working chamber 526.
A relief valve 630 is disposed in third chamber 527 of pump body 510, and is supported by a second spring 640 having a predetermined initial biasing force such that third oil path 524 is blocked off from fourth oil path 529 when relief valve is maintained in its initial position.
The operation of the conventional electromagnetic pump having a construction as described above is as follows.
When electric power is applied to the solenoid (not shown), a magnetic core (not shown) is magnetized so that the plunger assembly moves upwards. At this time, the volume of working chamber 526 is expanded so that the pressure in fifth oil path 555 connected thereto decreases. Thus, suction check valve 550 is opened and exhaust check valve 560 is closed, while oil is supplied to inlet portion 512 of pump body 510 from an oil tank through suction path 532 of connecting pipe 530. Some of the supplied oil fills up both first chamber 516 and third chamber 527 through first and fourth oil paths 514 and 529 respectively, and the remaining oil passes through suction check valve 550 disposed in second chamber 520 via filter 540.
Meanwhile, when the electric power applied to the solenoid is cut-off, the magnetic force applied to magnetic core is released so that the plunger assembly moves downwards. At this time, the volume of working chamber 526 is compressed so that the pressure in fifth oil path 555 interconnected thereto increases. Accordingly, suction check valve 550 is closed and exhaust check valve 560 is opened, while the oil pressurized in working chamber 526 is passing through exhaust check valve 560. At the same time, as shown in FIG. 7, the oil pressure starts increasing from initial pressure P1. Some of the pressurized oil having passed through exhaust check valve 560 flows through second oil path 522 into a space 518 formed between a side wall of first chamber 516 and an inner wall of pressure control plunger 570, and the rest flows into the front of relief valve 630 through third oil path 524.
As the up and down movement of the plunger assembly is repeated, the pressure of oil having flowed into space 518 through second oil path 522 continues to increase more and more so that pressure control plunger 570 is pushed backward while compressing a first spring 610. At the same time, as shown in FIG. 7, the pressure of oil also continues to increase from an initial pressure P1 to a second pressure P2. The oil having second pressure P2 can be normally evaporated and easily burned by the burner. In this way, the pressure of oil can be firstly controlled by pressure control plunger 570, and an oil having a controlled pressure can be exhausted to the burner when the burner is ignited and thereby the loud noise can not be generated.
When pressure control plunger 570 is moved up to a position where a protuberance 576 of pressure control plunger 570 contacts a projection 590 of cover 600, pressure control plunger 570 does not control the pressure of oil in the pump 500 any more. From this point, as shown in FIG. 7, the pressure of oil continues to increase from second pressure P2 to normal exhaust pressure P3.
When the pressure of oil having been increased by the repetition of the up and down movement of the plunger assembly exceeds the normal exhaust pressure P3, relief valve 630 is pushed backward while compressing second spring 640. At the same time, third oil path 524 and fourth oil path 529 are interconnected to each other so that some of pressurized oil over normal exhaust pressure P3 is returned to inlet portion 512 through fourth oil path 529 so as to decrease the pressure of the pressurized oil. Meanwhile, when the pressure of the pressurized oil in pump 500 decreases below normal exhaust pressure P3, relief valve 630 moves forward again so that fourth oil path 529 and third oil path 524 are blocked off again from each other. In this way, when the pressure of oil in pump 500 increases above the normal exhaust pressure P3, relief valve 630 moves backwards so as to interconnect third and fourth oil paths 524 and 529 with each other, and when the pressure of the pressurized oil in the pump 500 decreases below normal exhaust pressure P3, relief valve 630 moves forwards again to block off fourth oil path 529 and third oil path 524 from each other. As the above process is repeated continuously, the pressure of pressurized oil in the pump 500 is maintained almost constant and the pressurized oil having normal exhaust pressure P3 is exhausted to the burner.
In short, in conventional electromagnetic pump 500 as described above, the pressure of pressurized oil can be controlled in two steps by means of pressure control plunger 570 and relief valve 630 so that the loud noise, which is generated due to exhaust of the high pressurized oil to the burner when the burner is ignited, can be prevented.
However, the conventional electromagnetic pump 500 constructed as described above has the following disadvantages.
First, it necessarily requires pressure control plunger 570 for controlling the pressure of oil, first chamber 516 for accommodating pressure control plunger 570, separate relief valve 630 for secondly controlling the pressure of the pressurized oil and a separate element such as a buffer 620 for reducing pulsation of the pumped oil so that the volume of pump body 510 of the electromagnetic pump 500 is large, the weight of electromagnetic pump 500 is heavy, and its manufacturing cost increases.
Further, when the pressure of oil having been increased exceeds normal exhaust pressure P3, some of the pressurized oil is returned to inlet portion 512 of pump body 510 and is re-circulated in pump 500 in order to control the pressure of the pressurized oil. Therefore, there is waste of energy in re-circulating redundant oil.
Furthermore, it can not overcome the problem of the conventional electromagnetic pump as described hereinbefore. That is, it also uses a spring to block an oil exhaust path, and a biasing force of the spring is so weakly predetermined that the oil exhaust path is blocked-off belatedly after the operation of the pump 500 has finished. Accordingly, the oil of low pressure may be leaked to the burner even after the operation of the pump has been finished. The leaked oil having a low pressure is incompletely burned in the burner and thereby generates a bad smell.
On the other hand, a U.S. patent application with regard to an electromagnetic pump having a simple construction, in which the quantity of exhausted oil can be controlled in proportion to the pressure applied thereto and the incomplete combustion of oil can be avoided, has been filed by the applicant of the present invention and now is pending as U.S. Ser. No. 08/412,336.
The above electromagnetic pump has an exhaust control valve for overcoming the above problems. The exhaust control valve comprises a conical head, tapered cylindrical body and a guide tail. In the above electromagnetic pump, the exhaust control valve is disposed in an exhaust chamber interconnected to an oil exhaust path, and a rear end of which is supported by a spring having an initial biasing force such that the conical head of the exhaust control valve can close the exhaust path of oil when the exhaust control valve is maintained in its initial position.
In this state, the pressurized oil is flowed into the exhaust chamber according to the reciprocating movement of a plunger assembly, and the pressure in the exhaust chamber increases as the reciprocating movement of the plunger assembly is repeated. Then, when the increased pressure of oil exceeds the initial biasing force of the spring supporting the rear end of the exhaust control valve, the exhaust control valve moves backwards while compressing the spring, and when the pressure decreases below a second biasing force (i.e., biasing force of compressed spring), the exhaust control valve is moved forward again. The second biasing force is equivalent to a normal exhaust pressure P3 of oil and can be indirectly adjusted by adjusting the initial biasing force of the spring with an adjuster. The exhaust control valve repeats the above process in proportion to the pressure thereof so that the pressure of the exhausted oil can be maintained constant.
Meanwhile, when the operation of the electromagnetic pump has finished, the exhaust oil path can be blocked off quickly by the spring having a relatively strong biasing force so that the incomplete combustion of oil, which is caused by the leakage of oil having a low pressure to the burner, can be prevented.
However, the exhaust control valve having construction as described above can not completely overcome the loud noise problem since the oil having normal exhaust pressure P3 is exhausted so early that the high pressurized oil, even though it has a slightly reduced pressure, is still being supplied to the burner when the burner is ignited.
Accordingly, there is a need to provide an electromagnetic pump in which the loud noise problem can be completely solved, the construction can be simplified, energy efficiency can be improved, and incomplete combustion of oil can be prevented.